The manufacture of external parts of a timepiece is often accomplished using noble metals, such as gold or platinum, so as to ensure excellent resistance to corrosion. However, these metals are of high density, and the timepieces thereby made, particularly watches, are very heavy for the user, and are also expensive. A material such as gold is malleable, and its mechanical qualities are average, which often means that it is necessary to select gold alloys, which are more resistant, but also more susceptible to corrosion, with variations in appearance over time.
JP Patent Application No 60228666A in the name of CITIZEN describes the brazing of gold or gold alloy components on a titanium or titanium alloy base, and uses a TiN surface obtained by nitriding to stop the gold penetrating the titanium.
JP Patent Application No 56105881A in the name of SEIKO describes the brazing of gold or gold alloy components on a copper alloy base.
EP Patent Application No 1439434A1 in the name of CITIZEN discloses the brazing of components on a titanium base.